Although the cultivated grape (Vitis vinifera L.) is not a tropical plant, commercial viticulture is on the increase in many tropical areas. The diminished productivity of introduced higher latitude cultivars is offset by the possibility of two crops in one year. However, lack of adaptedness to relatively short day-lengths and high humidity generally results in fruit of poor quality.
By and large, available non-tropical grape varieties commonly suffer delayed, incomplete and irregular ripening, attended by inadequate levels of sugar, acidity and color. This can be compounded by cracking and rotting of unripe berries following rain. Foliage and developing fruit of vinifera type grapes are especially susceptible to various mildews and other fungus maladies in tropical environments.
Remedial techniques such as the use of growth regulators to increase budbreak, loosen clusters and improve ripening, as well as intensive spray schedules with fungicides, are costly imperatives that keep tropical viticulture from becoming competitive in the world market. Alternatively, the development of better adapted grape varieties through selective hybridization with native tropical species is a promising approach not widely practiced because of the considerable time-span required to raise and evaluate a single generation of hybrid progeny. The invention is an early product of a research and development program begun in 1966.